The bon bon is a perfect time capsule from the turn of the century, as saccharine-sweet 90s cocktails learned new tricks, using citrus and more varied spirits for balance. This one hails from lab bar in london circa 2001, before it was perfected by mixologist simon difford and added to diffords guide (an awesome resource for all cocktails, and especially butterscotch cocktails for some reason). It does taste like an english lemon-vanilla bon bon, with butterscotch providing a pleasant doughy note. The original recipe called for vanilla vodka, though difford uses plain vodka and a vanilla syrup in its place. This keeps the sweetness more controllable, since vanilla vodkas are all over the map in sugar content. You could still use your favorite vanilla vodka, but proceed carefully when adding simple or vanilla syrup.